1. Field of the Invention
The present invention relates generally to the field of fire retarding additives, and more specifically to a SiO.sub.2 based, powder mixture which may be added to paint to provide a fire retarding effect.
2. Prior Art
The prior art is rife with fire retardant compositions. The preferred fire retardant would be formulated from a basic abundant mineral, would be biologically and environmentally benign, would react to high temperature by expanding to form a protective layer and would be immune to burning at even extremely high temperatures. Moreover, the preferred fire retardant would be a suitable additive to coatings such as paints to provide walls, roofs and the like with fire protection.
A search of the prior art has revealed the following U.S. Patents which are relevant to the present invention:
U.S. Pat. No. 3,892,577 Sugahara et al PA0 U.S. Pat. No. 3,983,040 Draganov PA0 U.S. Pat. No. 4,226,838 Boros et al PA0 U.S. Pat. No. 4,347,331 Self PA0 U.S. Pat. No. 4,514,326 Sallay PA0 U.S. Pat. No. 4,838,941 Hill PA0 U.S. Pat. No. 4,843,103 Albertelli et al PA0 U.S. Pat. No. 4,900,698 Lundsager PA0 U.S. Pat. No. 4,992,321 Kandachi et al PA0 U.S. Pat. No. 5,153,657 Yu et al
Of the foregoing, the following appear to be most pertinent:
U.S. Pat. No. 4,843,103 to Albertelli et al is directed to foamed plastic materials. The foamed resinous product having excellent fire resistance uses at least 20% by weight of a finely divided inert and insoluble particulate solid, products capable of being employed as wood-substitutes or obtained when a dihydric compound is included in the mixture and the solid is talc, flyash and/or hydraulic cement. Any finely divided particulate solid which is insoluble in the reaction mixture appears to be suitable, provided it is inert and does not act as a blowing agent. Examples are clays, clay minerals, talc, vermiculite metal oxides, refractories and mineral fibers. Magnesite is also included.
U.S. Pat. No. 4,992,321 to Kandachi et al is directed to heat resistant foamed glass. Preferred examples of foliaceous or flaky filler materials are shale flakes, slate flakes and chlorite flakes. Mica vermiculite and kaolin may also be used. Preferred examples of fibrous filler materials are wollastonite and asbestos represented by chrysotile. A preferred example of non-metallic powdery or granular filler materials is pyrophyllite. It is also possible to use alumina, in particular corundum or a mineral of high alumina silicate type such as feldspar, zircon, cordierite, mullite or sillimanite. Talc may also be included.
U.S. Pat. No. 4,514,326 to Sallay is directed to a permanent flame retardant and anti-smoldering composition. The following are given as examples of tetraborates which may be employed in the practice of the present invention: tincal or borax, kernite or rasorite, tincalconite or borax pentahydrate, ulexite or boronatrocalcite and the industrially produced anhydrous borax.
U.S. Pat. No. 3,892,577 to Sugahara et al is directed to a white pigment excelling in resistance to flame and corrosion. In one embodiment of the invention, a white pigment is provided consisting of zirconium phosphate of the formula ZrO. (0.4-1.0) P.sub.2 O.sub.3, such zirconium phosphate containing at least 0.1% of a water soluble component. Zirconium phosphate, which is used in the invention as a flame resistant and corrosion resistant white pigment, can be prepared in the following manner: the starting zirconium material used as either an acid solution thereof obtained by melting a concentrate of zirconium minerals such as zircon sand and baddeleyite with an alkali, as required, to vitrify the zirconium material and thereafter dissolving same in a mineral acid such as sulfuric, hydrochloric, or nitric; zirconium chloride obtained in an intermediate stage of the so-called Kroll method may also be used.
U.S. Pat. No. 4,347,331 to Self is directed to a foamed, low density, highly extended unsaturated polyester resin syrup composition, a shaped article comprised of the composition and a process for preparing such article. The shaped article contains magnesite, mullite and vermiculite.
U.S. Pat. No. 4,838,941 to Hill describes a magnesium cement comprising talc, vermiculite and magnesite. U.S. Pat. No. 4,900,698 to Lundsager describes a ceramic product and process containing talc, vermiculite and mullite. U.S. Pat. No. 5,153,657 to Yu et al discloses a cleaning blade wear life extension by inorganic fillers reinforcement which contains quartz, diaspore, anatase, rutile and ilmenite. U.S. Pat. No. 4,226,838 to Boros et al discloses a process for accelerating the digestion and sedimentation steps of the Bayer alumina process which also comprises quartz, diaspore, anatase, rutile and ilmenite.
None of the aforementioned prior art has all of the features of the preferred fire retardant of the present invention.